1. Field of the Invention
The present invention relates to an antenna sense circuit and a related digital radio receiver, and more particularly, to an antenna sense circuit and a related digital radio receiver capable of improving voltage drops and a startup current.
2. Description of the Prior Art
Digital radio systems have been applied to automotive products as well as handheld products with an increasing trend, such as: a digital audio broadcasting (DAB) technology, a satellite radio technology, and Media FLO technology. Generally speaking, a digital radio product usually needs a set of antenna sense circuit used for providing power supply, system information, and error detections to an external antenna.
Currently, there are two kinds of antenna sense circuits widely adopted in the digital radio products. The first kind of antenna sense circuit is a simple diode current detecting circuit. As the name implies, it makes use of a diode to detect a startup current in order to determine whether an external antenna is coupled to the digital radio product. Such circuit has advantages of simple designs and low cost, but it has disadvantages of insufficient startup currents and exceeding voltage drops of diodes. The second kind of antenna sense circuit is a comparator current detecting circuit. Such circuit does not have the problem of exceeding voltage drops of diodes and it has advantages of adjusting the magnitude of the startup current, but it has a complicated circuit and costs too much.
Hence, how to improve the problems of voltage drops and the startup current, simplify circuits, and save cost have become an important topic of this field.